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Monday, 13 February 2017

HTZ-16: Improvisation on an Industrial Scale

Improvised armour vehicles appeared during WWI, but the phenomenon became truly commonplace during the Spanish Civil War. The most common type of vehicle was the improvised armoured car, but armoured tractors were also built. Less mobile than wheeled armoured cars, they were not in high demand in Spanish conditions. WWII triggered a resurgence of improvised armoured vehicles. The USSR built the largest amount of armoured tractors, and one of them, the HTZ-16, was accepted into production and built on an industrial scale. On July 20th, this vehicle turned 75 years old.

Anything for the Front, Anything at All

The Germans delivered a crushing blow to the Red Army in the first three weeks of Operation Barbarossa. In a short time, the army lost over half of its tanks. Most of them were considered obsolete, and their replacements were just entering production. However, brand new KV and T-34 tanks were also among those lost. Production plans were radically increased almost immediately after the start of the war. The issue was that plans look good on paper, but increasing production was a difficult case, especially with light tanks. According to pre-war plans, the main light tank of the Red Army was going to be the T-50. However, production was just beginning, and the situation with engines for these tanks was far from ideal.

The T-50's engine was produced at factory #75 in Kharkov. Factory #183, the main producer of the T-34 tank, was also located here. The Kharkov Tractor Factory (HTZ) was also positioned nearby, a major producer of agricultural tractors. The SHTZ-NATI tractor, developed in 1935 by the Agricultural Tractor Research Institute (NATI) was being built here since 1937. This vehicle was also used as an artillery tractor. Using the SHTZ-NATI design, Soviet designers created a custom transport tractor, which was mass produced under the index STZ-5.

Despite a similar purpose to tank factories, HTZ was not considered for tank production in 1941. It was also not considered when the war began, since the factory had to be radically converted to produce the light T-50. Especially since, as mentioned above, issues with engine production limited the availability of this tank. GKO decree #124 was issued on July 13th, 1941, ordering all equipment from the new plant at HTZ to be sent to Stalingrad to be installed at the Stalingrad Tractor Factory.

SHTZ-NATI tractor, the chassis for the HTZ-16.

Meanwhile, HTZ and NATI staff found a way to help the Motherland in its time of need. It is not known whether or not this was the initiative of NATI/HTZ staff or the military. Most likely, the proposal came from the factory.

NATI began working on a project to revive ideas of the early 1930s. A family of tracked armoured vehicles was developed on tractor chassis, including SPGs. The designers took the same road. Work was managed by V.Ya. Slonimskiy, the former lead of the SHTZ-NATI project, and E.G. Popov, who later invented the NATI D (Ya-11) tractor. A.M. Cherepin and A.V. Sapozhnikov also participated in the project. The latter was a tractor test driver.

The technical project of an armoured tractor on the SHTZ-NATI platform was completed and submitted for approval by the People's Commissar of Medium Production, V.A. Malyshev, in the middle of the month. The proposal was approved and Malyshev sent Stalin a draft for a GKO decree to order production of 2000 vehicles. There is information regarding GKO decree #019 "On the applique armour for light tanks and armouring of tractors". Allegedly, it assigned production of armoured tractors to HTZ and STZ, but that does not match reality.

For starters, the GKO decree signed on July 20th, 1941, had the number 219ss (top secret) and was titled "On production of 2000 armoured tractors". It also never mentioned STZ. Armoured tractors were to be produced exclusively in Khrakov. According to established deadlines, the first 50 tractors would be completed in August, then 850 in September, and 1100 in October. In addition, the decree did not mention the development of the tractor, but putting it into production.

The information that, allegedly, one tractor out of four was chosen in August. GKO decree #219ss clearly describes not only the chassis (SHTZ-NATI) but also the tactical-technical characteristics of the armoured tractor. The vehicle was armed with a 45 mm gun and a coaxial DT machinegun. The front armour was 30 mm, side armour was 13.5 mm. The tractor would have a top speed of 18-20 kph on roads and up to 10 kph off road.

One Month without Armour

The index HTZ-16 was already in use in early August of 1941. By then, NATI and HTZ began working on putting the armoured tractor into mass production. Chief Designer M.S. Sidelnikov headed the efforts from HTZ's side. The expectation was that two prototypes would be ready by August 12th, but in reality only one was completed. Due to a lack of 13 mm armoured plates, the sides were 10 mm thick. The rest of the hull wasn't made from armour at all, but from boiler plate.

Experimental HTZ-16 prototype, August 1941.

By the time the experimental vehicle entered trials, HTZ was already hard at work making chassis from the armoured tractor. There are mentions of the STZ-3 serving as a chassis for the HTZ-16, but that information is incorrect. The technical description of the vehicle clearly stated that it was based on the SHTZ-NATI agricultural tractor. However, changes to 27 components had to be made to use it as an armoured tractor. This is not surprising, as the SHTZ-NATI was not suitable for a fighting vehicle due to its big-nosed layout and tight crew compartment. A change in layout and redesign of several components was necessary.

For one, the power of the 1-MA engine was increased from 52 to 58 hp. This is not much, but the mass grew from 5.1 to 8.6 tons, and every extra horse power was needed. The gearbox was also changed to handle the extra mass and engine power. The frame was lengthened, with the bogeys positioned like on the STZ-5 and idlers that were further forward. The designers also used track links from the STZ-5, since they were more suitable for a combat vehicle. The fuel tank was shifted to the left, freeing up the space for the driver in front and to the right of his former position. These rearrangements opened up room for a fighting compartment which housed two more crew members.

The front armour plate was attached with bolts to make service easier.

An armoured hull was installed on the chassis with armour that was sloped as highly as possible. This was only partially possible, as the SHTZ-NATI was not very large (3451 mm in length without the starter handle). The HTZ-16 was not much larger than its predecessor, 3830 mm in length, 1870 mm in width, 2300 mm in height. The front armoured plate (in front of the engine) was 30 mm thick at a slope of 20 degrees. The armoured plate on the front of the fighting compartment was sloped at 25 degrees. The tractor was protected from the front against high caliber machineguns and autocannons. This was not enough to protect from anti-tank guns, but other Soviet light tanks short of the T-50 had thinner armour.

Despite its tractor chassis, the HTZ-16 was hardly archaic. The issue of observation was resolved as well as possible, the hull was welded, the issue of hatches was handled well. The 45 mm cannon and DT machinegun matched the requirements for light tanks at the time. The problem was that the gun was already obsolete by 1941.

A hatch was added on the driver's side.

The uniqueness of the HTZ-16 was not only in its title of the most numerous armoured tractor in history. This tank was put through a full program of trials, both mobility and ballistic. According to initial plans, the HTZ-16 was to travel 500 km. The prototype drove for 470 km, 240 of it on a cobblestone road, 69 on a leveled dirt road, 139 km on a country dirt road, and 22 through other road conditions. This is a lot for an ersatz vehicle. The average highway speed was 17 kph, the range was 119 km. Off-road, the average speed was 8.9 kph, with a range of 61 km.

Trials showed that the engine, which drew air from the fighting compartment, overheated. This was not surprising, given the vehicle's increased mass and the fact that the outdoor temperature was almost 30 degrees Celsius. During mobility trials, the tractor crossed a 25 degree slope, which isn't bad for an improvised vehicle. Maximum tilt was 24 degrees. The tractor could cross a 1.3 meter deep trench, 55 cm tall wall, and ford a 0.6 m deep river. The engine stalled at high grades, but this issue could be solved by topping up the fuel tank. There were also instances of broken track links.

The fighting compartment was accessed through a large hatch in the rear.

The ballistics trials were also large in volume. 247 shots were fired, 147 of them with armour piercing shells. The precision of the gun was less than calculated, which was blamed on looseness in the gun mount. The average rate of fire was 5 RPM. The gun mantlet caused complaints, as it allowed bullets and shrapnel to enter the vehicle.

45 mm gun and DT machinegun mount in a HTZ-16.

Overall, the military did not like the armoured tractor, which is not surprising. Demands were made to begin production of proper tanks urgently. In addition, GKO decree #222 was signed on July 20th, 1941, tasking HTZ with production of T-60 tanks. However, as they say in Odessa, wishes and abilities are two different things. Incidentally, the armoured tractor borrowed some parts from the T-60, including its observation devices.

By August 18th, HTZ was still receiving documentation for the T-60, but 329 HTZ-16s were present in various states of readiness. However, none of them had tracks or electrical equipment. The factory had 1037 chassis by August 30th, but the condition was critical. The chassis were not equipped with armoured hulls. The Voroshilovgrad and Novo-Kramatorsk factories were the suppliers of HTZ-16 and T-60 hulls, but neither sent a single hull before the end of August. The delay was explained by issues with hardening the armour.

A project to convert the STZ-5 into an armoured tractor. This idea by factory #264 engineers Krasilshikov and Nemchinskiy received no support.

The situation was so dire that the first 33 hulls were made from mild steel. 36 HTZ-16s were delivered by September 14th. By that time, 1528 chassis were gathered at HTZ, 717 of them with no tracks, 1334 with no fuel tanks, and 1304 without electrical equipment.

The first HTZ-16s, which GABTU correspondence also called T-16, left the factory on September 7th. The vehicles had numbers starting with 16 (16-001 and so on). Since the serial number depended on the chassis, some vehicles had numbers like 16-1672, even though only 142 armoured tractors were produced. GKO decree #681 ordering the evacuation of HTZ to Stalingrad was signed on September 16th. HTZ-16 production continued past that date, but nowhere near the volume of 2000 units.

Knocked out HTZ-16. The vehicle has camouflage paint.

As an aside, let us discuss the alleged production of the HTZ-16 in Stalingrad. For starters, HTZ did not completely evacuate to Stalingrad. A portion of the tractor manufacturing equipment ended up in Rubtsovks, Altai Krai. As for the tank production equipment, it was sent to factory #264, not STZ. Documents mention the presence of 45 mm guns and questions of what to do with them. Factory #264 didn't want to deal with armoured tractors, as they were tasked with production of T-60s in addition to T-34 hulls.

Factory #264 engineers Krasilshikov and Nemchinskiy wrote a letter to Stalin and the People's Commissar of Ship Production in mid-August, proposing the production of armoured tractors on the STZ-5 chassis at the factory. The response was negative.

A Short Age of the Armoured Tractor

According to existing documents, all HTZ-16s with mild steel hulls were sent to training units. They were not only sent to Kharkov: one armoured tractor each was sent to the schools at Ulyanovsk, Armavir, and Stalingrad. The first unit to receive tractors with armoured hulls was the 12th Tank Brigade, who received 14 HTZ-16s. Eight tractors were sent to the 14th Tank Brigade, one to the 13th Tank Brigade, and five to the 7th Tank Brigade. The unit that received the most HTZ-16s was the 133rd Tank Brigade: a whole 36 vehicles. The 47th Tank Division and 23rd Reserve Regiment received eight vehicles each. However, sending an armoured tractor didn't mean that it actually arrived. For instance, the 35th Tank Brigade was issued 8 HTZ-16s, but never received them.

Knocked out and partially burned HTZ-16. The vehicle has not only camouflage, but a unit emblem.

For obvious reasons, the HTZ-16 saw its first battles in and around Kharkov. On September 22nd, the 12th Tank Brigade was ordered to capture Krasnograd (Kharkov oblast). According to operation reports, the tractors fought against Italians. The 12th Tank Brigade fought for Krasnograd for several days, fierce fighting erupting in its streets. On September 27th, Soviet units were forced on the defensive, as the brigade took heavy losses in armour and personnel. HTZ-16s also fought in defense of Kharkov. One armoured tractor supported militia fighting near the ZUM on October 24th, 1941. The tractor was knocked out and its crew burned up.

This HTZ-16 survived 1941 and was only knocked out in the spring of 1942.

Most HTZ-16s were lost in the fall of 1941. However, a small number lived through 1941. Some vehicles were used in the battle for Kharkov in May of 1942. This was their last use in combat. The topic of HTZ-16s in combat in 1941-42 demands further study, which is made difficult by the fact that few documents remain from that time.

This image shows two types of tractors that the Germans built in Kharkov. The difference is not only in the cabins, but in the tracks.

It's too early to stop telling the story of the HTZ-16 here. As mentioned before, over 1500 HTZ-16s in various stages of completion were present at the factory. Not all were evacuated. Documents list 809 chassis left at the factory. Of course, the Germans didn't build armoured tractors. Not only did they not have any hulls for them, they were not in demand. However, the Germans were very interested in production of tracked tractors due to the fact that only tanks and halftracks could drive in the rasputitsa. The armoured tractors were converted back to regular tractors.

Their shape was very varied. Some of them were built like the SHTZ-NATI, with the same cabin as the original tractor, the others had stranger designs. There weren't enough STZ-5 tracks for all vehicles, so some used SHTZ-NATI tracks. Some tractors received original cabins for gun crews. Most subjects of this reverse conversion became artillery tractors.

ATZ-3T, an artillery tractor on the HTZ-16 chassis.

To conclude, there was another vehicle that was a direct descendant of the HTZ-16. As mentioned above, some of HTZ's equipment was evacuated to Rubtsovsk. This equipment was used to build the Altai Tractor Factory (ATZ), with the same Sidelnikov as the chief designer. The factory produced its first tractor, indexed ATZ-NATI, in August of 1942.

Meanwhile, the country needed tractors like the STZ-5, not agricultural tractors. The ATZ design bureau designed such a tractor in 1943. This vehicle was indexed ATZ-3T, and used many technical solutions from the HTZ-16, including the fuel tank to the left and driver to the right. This solution freed up space for a small truck bed. The engine on this tractor was also supercharged to 58 hp. According to documents, one prototype was built in the summer of 1943. GAU Chief, Colonel-General Yakovlev, suggested that ATZ build a trial batch of tractors on July 1st, 1943, but by that time the superior Ya-11 tractor was already in production. That was the end of this vehicle's story.